 //创建继承 Person 的 Student 子类
 function Person(name, chinese, math) {
     this.name = name
     this.chinese = chinese
     this.math = math
 }

 function Student(name, chinese, math, age) {
     Person.apply(this, [name, chinese, math])
     this.age = age
     this.show = function () {
         return "姓名:" + this.name + "<br>语文成绩:" + this.chinese + "<br>数学成绩:" + this.math + "<br>年龄:" +
             this.age + ""
     }
 }
 Student.prototype = new Person()
 Student.prototype.constructor = Student
 let stu = new Student("张三", 98, 80, 25)
 app.innerHTML = stu.show()